Adsorbent filters are widely utilized in such industries as the electronics industry and the pharmaceuticals industry. For example, in the computer industry, adsorbent filters are positioned within disk drives, to protect the disk drives from water vapor hydrocarbons and/or acid gases. Without such protection, these vapors can lead to stiction, corrosion and, ultimately, drive failure.
In general, adsorbent filters comprise a porous construction having positioned therein adsorbent. Arrangements presently widely used comprise granular or powdered adsorbent, for example desiccant and/or carbon adsorbent, enclosed within a pouch. Such an arrangement is described, for example, in U.S. Pat. No. 4,830,643 to W. L. Gore & Associates, Inc. The arrangements described in the '643 patent comprise a tubular container of porous polytetrafluoroethylene sealed at each end so as to enclose adsorbent particles. Among the materials described in the '643 patent as the adsorbent particles, are silica gel (SG), activated carbon, calcium sulfate, calcium carbonate, activated alumina and molecular sieve adsorbent.
Alternate constructions to those described in the '643 patent have been available from Donaldson Company, Inc. of Bloomington, Minn., the assignee of the present invention. The Donaldson constructions generally comprise a pouch comprising two sheets of polytetrafluoroethylene membrane, sealed to one another along a border or perimeter seal. Enclosed within the pouch is the particulate adsorbent material. In some constructions, a second pouch is enclosed within the first pouch, and the second pouch contains the adsorbent material. In either case, in the past in such constructions, the adsorbent material has typically comprised a loose, granular, flowable, solid material.